Public key cryptography, combined with the traditional symmetric cryptograph and the message digest technology, can provide confidentiality, integrity and proof of origin.

公钥密码技术结合传统的对称密码技术及信息摘要技术，可提供信息的保密性、完整性和信源确认，是多种安全应用的基础。

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For instance, proof of the origin of much of the gold in Swiss banks was provided only a few weeks ago when German Reichsbank records, at first thought lost, were discovered.

ECONOMIST: Switzerland and the Jewish gold

Given the ease with which proof-of-origin papers can be faked, it was hard to tell where any of it really came from.

ECONOMIST: Genetic testing of wood can curb illegal logging

Because the sounds of the most closely related apes matched most closely in the analysis of the laughter, the researchers believe the work is proof of laughter's shared evolutionary origin, followed by adaptation to its form in the species we see today.

BBC: Tickled apes yield laughter clue